defrost is extremely hot

[e.caden]

Hello guys

When I push the defrost button on my 95 740il it blows high heat only, no matter what I adjust the temperature to with the a/c on - I've noticed that the temperature cluster on the instrument panel reads -40C for the outside reading - are these related? Is there anyway I can fix this myself?
It wasn't a problem while living in Chicago, but now I'm in Houston and when it rains the defrost is killing me!!!!!

[Qsilver7]

If you do...you should take a look at the pages that discuss the heating/ac functions. It explains that the defrost button is for rapid defrosting and your system is operating as it should. It also explains how to demist the windows if you want to use a more "controlled" air temp approach.

If you don't have an owners manual...you can download or read it on site at: http://www.e38.org ... although there isn't a 1995 owners manual...the 1997 manual will cover the same and operate the same as your 1995.

Good luck. :)

Edit: below you will see some exerts from the owners manual that describes the HVAC buttons. To defrost/demist condensation on the interior windows with "controlled" air...you use the button with the upward arrow that indicates air distribution to the windshield.

Edit 2: you may also want to pay attention to if you have the recirculation button pressed. Recirculating the cabin air shuts off fresh air flow thru the system...this can also build up condensation in the cabin. Experiment with breathing into a plastic bag and - you'll see water droplets form inside the bag...if you get light headed...you may want to remove it from your head before you pass out! :D If you are having this experience...turn the recirculation button off.

[e.caden]

QSilver7

Thanks for the advice, I didn't have a 95 manual and this instructions were great. All is well with the defrost on the vehicle.

[M.Wong]

In addition to Q's great information, -40 means your outside temperature sensor is likely bad, not connected, or gone. Check for it and replace if necessary. With a -40 reading, your heat and A/C will not work right.
(The A/C will not come on because the car thinks it's chilly outside.)

Remove the main lower splash guard in the center then the smaller splash guard that fits just outboard (driver's side) of the main splash guard. Once removed you should be able to see the brake duct. Sticking out of the side of it is the temp sensor.

Link:
Looks like part number 3 (http://www.realoem.com/bmw/showparts.do?model=GH83&mospid=47531&btnr=65_0519&hg=65&fg=05) 65-81-6-905-133

[Bread]

Edit 2: you may also want to pay attention to if you have the recirculation button pressed. Recirculating the cabin air shuts off fresh air flow thru the system...this can also build up condensation in the cabin. Experiment with breathing into a plastic bag and - you'll see water droplets form inside the bag...if you get light headed...you may want to remove it from your head before you pass out! :D If you are having this experience...turn the recirculation button off.

The recirculation setting automatically turns off when I switch on the defroster in my '01.

[Qsilver7]

Edit 2: you may also want to pay attention to if you have the recirculation button pressed. Recirculating the cabin air shuts off fresh air flow thru the system...this can also build up condensation in the cabin.


The recirculation setting automatically turns off when I switch on the defroster in my '01.
it does the same on mine, too...but since he was originally not using the HVAC button that blows (conditioned) air onto the windshield (he was using the rapid defrost button which goes to high and uses only heat)...he could be getting condensation on his windows because he has the recirc feature on...if this were tru....then he could stop the condensation from forming by turning off recirc. :)